The present invention relates to a recordable/reproducible optical disk, in which information pit arrays of sector addresses are disposed so as to wobble between a land track and a groove track; and an optical disk recording/reproduction apparatus for performing recording and/or reproduction for the optical disk.
Optical disks have excellent removability/portability and random access performance. Therefore, it has become more and more prevalent to employ optical disks as memories in various information equipment fields, e.g., personal computers. As a result, there has been an increasing demand for increasing the recording capacitance of optical disks.
In general, guide grooves for tracking control purposes are formed on rewritable optical disks, so that data is recorded and reproduced by utilizing the guide grooves as tracks. In addition, a track is divided into a plurality of sectors for sector-by-sector management of data. Therefore, in the production of such disks, address information for each sector is often formed in the form of pits while forming the guide grooves.
In currently prevalent rewritable optical disks, tracks for recording data are either the grooves formed during the disk formation (grooves) or the interspaces between grooves (lands). On the other hand, optical disks of a land-groove recording type for recording data on both the grooves and the lands have also been proposed.
FIG. 22 illustrates an exemplary optical disk of the land-groove recording type. As used herein, the portions which are located closer to the optical disk surface are referred to as xe2x80x9cgroovesxe2x80x9d, whereas the portions which are located further away from the optical disk surface are referred to as xe2x80x9clandsxe2x80x9d, as shown in FIG. 22. It should be noted that xe2x80x9clandsxe2x80x9d and xe2x80x9cgroovesxe2x80x9d are mere names; therefore, the portions which are located closer to the optical disk surface may be referred to as xe2x80x9clandsxe2x80x9d, while the portions which are located further away from the optical disk surface may be referred to as xe2x80x9cgroovesxe2x80x9d.
An optical disk of the land-groove recording type requires sector addresses for both the lands and the grooves. In order to facilitate the process of forming address pits on an optical disk, an intermediate address method has been studied in which address pits are formed between a land and a groove adjoining each other so that the same address is shared by the adjoining tracks (Japanese Laid-Open Publication No. 6-176404).
Hereinafter, the intermediate address, a tracking control method for reading information from an optical disk, and a method for reading signals from an intermediate address will be described with reference to the figures.
FIG. 23 is a schematic diagram showing an optical disk having a sector structure. In FIG. 23, reference numeral 200 denotes a disk; reference numeral 201 denotes a track; reference numeral 202 denotes a sector; reference numeral 203 denotes a sector address region; and reference numeral 204 denotes a data region. FIG. 24 is a magnified view of a sector address region schematically showing a conventional intermediate address. In FIG. 24, reference numeral 206 denotes address pits; reference numeral 207 denotes recording marks; 208 denotes a groove track; reference numeral 209 denotes a land track; and reference numeral 210 denotes a light spot.
In the optical disk shown in FIG. 24, the groove 208 and the land 209 are employed as tracks. Data signals can be recorded by forming the recording marks 207 on the groove 208 and the land 209. The groove track 208 and the land track 209 have the same track pitch Tp. The center of each address pit 206 is shifted by Tp/2 from the center of the groove track 208 along the radius direction. In other words, each address pit 206 is centered around the boundary between the groove 208 and the land 209. Although the lengths or intervals of the address pits 206 are modulated by an address signal, FIG. 24 only schematically illustrates the shapes of the address pits 206.
FIG. 25 is a block diagram showing the conventional tracking control and the signal processing for reading signals on an optical disk.
The structure shown in FIG. 25 will be described below, In FIG. 25, reference numeral 200 denotes a disk; reference numeral 201 denotes a track; reference numeral 210 denotes a light spot; and reference numeral 211 denotes a disk motor for rotating the disk 200. An optical head 212 optically reproduces a signal on the disk 200. The optical head 212 includes a semiconductor laser 213, a collimation lens 214, an object lens 215, a half mirror 216, photosensitive sections 217a and 217b, and an actuator 218. A tracking error signal detection section 220 detects a tracking error signal indicating the amount of dislocation between the light spot 210 and the track 201 along the radius direction. The tracking error signal detection section 220 includes a differential circuit 221 and a LPF (low pass filter) 222. A phase compensation section 223 generates a drive signal from a tracking error signal for driving the optical head. A head driving section 224 drives the actuator 218 in the optical head 212 in accordance with the drive signal.
An address reproduction section 234 includes an addition circuit 225, a waveform equalization section 226, a data slice section 227, a PLL (phase locked loop) 228, an AM detection section 229, a demodulator 230, a switcher 231, and an error detection section 232. The addition circuit 225 adds signals from the photosensitive sections 217a and 217b. The waveform equalization section 226 prevents the inter-sign interference of a reproduced signal. The data slice section 227 digitizes the reproduced signal at a predetermined slice level. The PLL (Phase Locked Loop) 228 generates a clock which is in synchronization with the digitized signal. The AM detection section 229 detects AMs (address marks). The demodulator 230 demodulates the reproduced signal. The switcher 231 separates the demodulated signal into data and an address. The error detection section 232 performs an error determination in the address signal. An error correction section 233 corrects errors in the data signal.
Hereinafter, an operation for tracking control will be described. Laser light radiated from the semiconductor laser 213 is collimated by the collimate lens 214 and converged on the disk 200 via the object lens 215. The laser light reflected from the disk 200 returns to the photosensitive sections 217a and 217b via the half mirror 216, whereby the distribution of light amount is detected as an electric signal, which is determined by the relative positions of the light spot 210 and the track 201 on the disk. In the case of using the two-divided photosensitive sections 217a and 217b, a tracking error signal is detected by detecting a difference between the photosensitive sections 217a and 217b by means of the differential circuit 221 and extracting a low frequency component of the differential signal by means of the LPF 222. In order to ensure that the light spot 210 follows the track 201, a drive signal is generated in the phase compensation section 223 such that the tracking error signal becomes 0 (i.e., the photosensitive sections 217a and 217b have the same distribution of light amount), and the actuator 218 is moved by the head driving section 224 in accordance with the drive signal, thereby controlling the position of the object lens 215.
On the other hand, when the light spot 210 follows the track 201, the amount of reflected light is reduced at the recording marks 207 and at the address pits 206 on the track owing to interference of light, thereby lowering the outputs of the photosensitive sections 217a and 217b, whereas the amount of reflected light increases where pits do not exist, thereby increasing the outputs of the photosensitive sections 217a and 217b. The total light amount of the output from the photosensitive sections which corresponds to the recording marks 207 and address pits 206 is derived by the addition circuit 225, led through the waveform equalization section 226 so as to remove the inter-sign interference of the reproduced signal, and digitized at a predetermined slice level at the data slice section 227 so as to be converted into a signal sequence of xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d. Data and a read clock are extracted from this digitized signal by the PLL 228. The demodulator 230 demodulates the recorded data which has been modulated, and converts it into a data format which allows for external processing. If the demodulated data is a signal in the data region, the errors in the data are corrected in the error correction section 233, whereby a data signal is obtained. On the other hand, if the AM detection section 229 detects an AM signal for identifying the address portions in a signal sequence that is constantly output from the PLL 228, the switcher 231 is switched so that the demodulated data is processed as an address signal. The error detection section 232 determines whether or not the address signal which has been read includes any errors; if no error is included, the address signal is output as address data.
FIG. 26 shows the states of a reproduced signal (RF signal) and a tracking error signal (TE signal) when the light spot 210 passes the sector address region 203 in the above-described configuration. Although the light spot 210 is on the center of the track in the data region 204, a drastic dislocation occurs between the light spot 210 and the address pits 206 immediately after the light spot 210 enters the sector address region 203, thereby greatly fluctuating the level of the TE signal. The light spot 210 cannot rapidly follow the address pits but gradually comes closer to the address pits, as indicated by the broken line. However, since the sector address region 203 is short and the data region 205 (which is a grooved region) is reached before the light spot 210 manages to completely follow the address pits, a tracking control is performed so that the off-tracking becomes zero in the grooved region. The amount of off-tracking in the last portion of the sector address region is defined as Xadr. Moreover, since a portion of the light spot 210 is on the address pits 207, an RF signal as shown in FIG. 26 is obtained. The RF signal amplitude Aadr varies in accordance with the distance between the light spot 210 and the address pits 206. Specifically, Aadr decreases as the distance becomes larger, and increases as the distance becomes smaller.
In the case where the address pits of intermediate addresses are provided in only one direction along the radial direction, the distance between the light spot and the address pits may also vary in the sector address region in the case where the center of the light spot is dislocated from the center of the track in the data region. As a result, there is a problem in that, although the amplitude of the reproduced signal in the address pit region will increase if the light spot is shifted closer to the address pits, the amplitude of the reproduced signal in the address pit region will decrease if the light spot is shifted away from the address pits, thereby resulting in an insufficient reading of the address.
There is also a problem in that, since the synchronization of the read clock and the setting of the slice level for digitization are to be performed in the beginning portion of an address region, the reproduction of the beginning portion must become stable; otherwise proper demodulation cannot occur even if a reproduction signal is obtained elsewhere.
There is also a problem in that, since the light spot is dislocated from the address pits in the sector address region, a large fluctuation in level, which does not indicate the actual track offset amount, occurs in the tracking error signal. Since the tracking control is performed by using such a tracking error signal, a tracking offset may occur after the light spot has passed the sector address section.
There is also a problem in that, since the same address pits are read for a land track and a groove track adjoining each other, it is impossible to identify whether or not a track which is currently being followed is a land track or a groove track.
In view of the above-mentioned problems, the present invention has an objective of providing an optical disk having a novel address pit arrangement in sector address sections such that insufficient reading of address signals due to tracking offset is reduced and the tracking offset after passing a sector address is reduced, the optical disk further enabling identification of land tracks and groove tracks; an optical disk recording/reproduction apparatus employing such an optical disk; and an optical disk recording/reproduction apparatus including an ID detection circuit for optical disks capable of accurately detecting the locations and polarities of ID sections.
The optical disk recording/reproduction apparatus includes an apparatus for recording data on an optical disk, an apparatus for reproducing data recorded on an optical disk, and an apparatus for recording data on an optical disk and reproducing data recorded on an optical disk.
The optical disk according to the present invention is a land-groove optical disk including a plurality of sectors having a sector address and a data region, the sector address indicating a sector position, wherein the sector address includes a plurality of address blocks, at least four of the plurality of address blocks each containing an address number and an overlapping sequential number; each two of the at least four of the plurality of address blocks make a group; and the respective groups of address blocks are in an alternating arrangement from a track center between being shifted toward an inner periphery side and toward an outer periphery side, by a width substantially equal to half a track pitch, along a radius direction. As a result, the above-mentioned objectives are met.
The sector address may include a block containing information other than the address number and the overlapping sequential number; and the block may be disposed so as to be shifted from the track center toward one of the inner periphery side and the outer periphery side, by the width substantially equal to half the track pitch, along the radius direction.
The sector address may include at least two blocks containing information other than the address number and the overlapping sequential number; and the blocks may be disposed so that one of the at least two blocks is shifted from the track center toward the inner periphery side, and the other of the at least two blocks is shifted toward the outer periphery side, by the width substantially equal to half the track pitch, along the radius direction.
Preferably, a first pattern and a last pattern of each address block includes non-address pit data.
At least four of the plurality of address blocks may contain data of a clock synchronization signal; and data of the clock synchronization signal contained in a first address block of each group may have a length longer than lengths of the clock synchronization signals contained in other address blocks of the group.
An optical disk recording/reproduction apparatus includes: an optical head for radiating a light beam on the aforementioned optical disk and receiving reflected light therefrom to output a reproduced signal; an address signal reproduction section for reading the address numbers and the overlapping sequential numbers when reproducing the sector addresses of the optical disk; and an address correction section for correcting, with respect to each address block, the address numbers which have been read in accordance with the overlapping sequential numbers which have been read. As a result, the above-mentioned objectives are met.
Another optical disk recording/reproduction apparatus according to the present invention includes: the aforementioned optical disk; a tracking error signal detection section for detecting a tracking error signal indicating an offset amount between a track and a light spot; a timing generation section for generating gate signals in synchronization with the respective address blocks of the sector address; an outer periphery value sample-hold section for sampling and holding, in synchronization with the gate signal, a level of the tracking error signal with respect to an address block disposed on the outer periphery side; an inner periphery value sample-hold section for sampling and holding a level of the tracking error signal with respect to an address block disposed on the inner periphery side; a differential circuit for deriving a difference in values of the outer periphery value sample-hold section and the inner periphery value sample-hold section; and gain conversion section for converting the output of the differential circuit to a predetermined signal level. As a result, the above-mentioned objectives are met.
Still another optical disk recording/reproduction apparatus according to the present invention includes: the aforementioned optical disk; a reflected light amount signal detection section for detecting a reflected light amount from the optical disk; a timing generation section for generating gate signals in synchronization with the respective address blocks of the sector address; an outer periphery value sample-hold section for sampling and holding, in synchronization with the gate signal, a level of the reflected light amount signal with respect to an address block disposed on the outer periphery side; an inner periphery value sample-hold section for sampling and holding a level of the reflected light amount signal with respect to an address block disposed on the inner periphery side; a differential circuit for deriving a difference in values of the outer periphery value sample-hold section and the inner periphery value sample-hold section; and gain conversion section for converting the output of the differential circuit to a predetermined signal level. As a result, the above-mentioned objectives are met.
An optical recording/reproduction apparatus including an ID detection circuit for an optical disk according to the present invention includes: a tracking error detection circuit including split detectors for obtaining a tracking error signal for the aforementioned optical disk and a broad-band differential amplifier for outputting a differential component between detected signals from the split detectors as a tracking error detection circuit; an envelope detection circuit including a high pass filter for extracting a high frequency component of the tracking error signal, a full-wave rectifier for applying full-wave rectification to the high frequency component, a first low pass filter for extracting a low frequency fluctuation component of the full-wave rectified high frequency component, and a first comparator for comparing the low frequency fluctuation component and a reference voltage to output an ID envelope signal; a polarity detection circuit including a second low pass filter for extracting a second low frequency component from the tracking error signal, a third low pass filter for extracting a third low frequency component from the tracking error signal, the third low frequency component having a smaller band width than that of the second low frequency component, and a second comparator for comparing the second low frequency component and the third low frequency component to output an ID polarity signal; and a logic circuit for outputting a read gate and a land-groove identification signal from the envelope signal and the polarity signal. As a result, the above-mentioned objectives are met.